Conversion of hydrocarbon oils



J. W. WARD CONVERSION oF HYDROCAHBON o'Ls Filed Feb. 24, 1941 Aug. 15,1944.

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Patented Aug. 15, 14944 V umrizov STATES PATENT oFFlcE John W. Ward,Chicago, Ill., assignor to Universal ,Oil Products Company, Chicago,`I1l., -a`

Y corporation ofDelaware Y y -Y Application February 24,1941,SerialfNo`.` 380,127 solaims. (c1. 19e-48)",

This invention relates to an V'improved process for the pyrolytcconversion ofrhydrocarbon oils and is more particularly directed to acom` bination lprocess in which relatively heavy oils are cracked andlight distillates reformed,` to produce therefrom high yields of good'antiknock gasoline. l

lOne yspecific embodiment of the invention provided by the processcomprises, crackingrelatively high-boiling components at elevatedtemperature and substantial superatmospheric pressure, separating vaporsand non-vaporous residue from the resulting product, fractionating saidvapors to separate relatively high-boiling components therefrom asreflux condensate, returning said reflux condensate to the`aforementioned cracking step, lighter hydrocarbon oil, such asdistillate comlprising poor antiknock gasoline fractions, to reform andconvert the same into highyields of gasoline of `im-proved antiknockvalue, cooling the resulting reformed products sufficiently to preventsubstantial further cracking thereof and in a second fractionating stepfractionating the cooled products in commingled state with frac#tionated vapors from the first mentioned fractionating step to condensefrom the mixture, as a secondary Vreflux condensate, components thereofboiling above range of the desiredgasoline product, Asubjectingfractionated vapors kof the desired end-boiling point from `the secondmentioned fractionating step to condensation, recovering the resultingdistillate and cooling and commingling'regulated 'quantities of saidsecondary reflux condensate with'the heated products of the reformingstep to effect' said cooling of the latter.

As a special feature of the invention, that portion fof said secondaryreflux condensate, which is not required for cooling the reformedproducts, as abovedescribed, is subjected to flash distillation tosubstantially free the same of undesired low-boiling components to leaveas the unvaporized residue a product meeting market specifications forfurnace oil, the evolved vapors from kthis flash distilling step beingsubjected to condensation and the resulting condensate returned inregulated quantities to one or both of 1 the aforementionedfractionating steps wherein it serves as a refiuxing and cooling medium.This feature cooperates With the feature of subjecting the vaporousproducts of the heavy oilcracking operation to primary and secondaryfractionation in successive. fractionating zones and the .feature ofsupplying the reseparately heating a' formed products .to said secondaryfractionating zone in that, by this method of operation, materials ofthe generalnature of pressure distillate bottoms in the products of theheavy oil cracking operation and thetot'al componentsr of the reformedproducts boiling above the range of gasoline are recovered as anintermediate [product meeting the flash point and other specificationsfor good quality furnace oil.' These featuresV are also cooperative withthat of employing regulated quantities of said secondary refluxcondensate as a medium for cooling the hot reformed products prior tofractionation thereof. The secondary reflux condensate is ideal for thispurpose in that it 'is relatively refractory for cracking, Will notcontaminate the reformed products in any respect and in that, since itis not materially converted into lighter and heavier productsbyrecycling in the manner described and an unlimited quantity thereof isavailable for cooling the reformed products. Due to thesecharacteristics, its use inthe manner described does not appreciablydecrease th'e quantity of furnace oil recovered.

Another special and coperative feature of the invention resides insubjecting a regulated portion. of the fractionated vaporous stream fromthe primary fractionating zone to partial con. densation to form adistillate which is returned as cooling and reuxing medium to theprimary fractionating step, the uncondensed components of the lpartiallycondensed stream being commingled and subjected vto further condensationwith thefractionated vapors-from the secondary fractionatingzone. L Thisis not only a'convenient method of obtaining reluxing material for theprimary fractionator; but also materially decreases the load andrequired size of the secondary fractionator as compared with anoperation in which uncondensed components .of said partially condensedstream are supplied to the secondary fractonator or an operation inwhich the total fractionated vapors from the primary fractionator aresupplied to the secondary fractionator. In order to obtain fulladvantage of this feature, I operate the partial condensing andsucceeding separating step under temperature and pressure conditionsregulated to give acondensate `for recycling to the primary,fractionator as a cooling and refluxing mediumwhi'ch is substantiallyfree of Vdissolvedigases and" give an uncondensed fraction consistingpredominantly of light gasoline and gases andfsubstantially. free ofcomponents boiling above the range of the desired final gasolineproduct. kBy this'meth'odof operation, said uncondensed fractions willnotl Referring to the drawing, charging stock for the process, which maycomprise an oil `of high--V boiling characteristics or of relativelywide boiling range, such as, for example, crude petroleum",

topped crude or the like, is supplied vthrough line I and valve 2 topump 3 by means of which it is fed through line 4 and may be directedthere-Y from, all or in part, through line `and valve 6 intofractionator 1 or, allor in part, through' lineV 3, valve `9 and line I0to heating coil II.

Y .When the charging oil isY supplied, as described, tofractionator 1,it serves as aI cooling and reuxin-g medium in this zone for thevaporous conversion products with which it is commingled therein and issubjected to fractionation with the vapors. Any components of the chargeoil supplied to fractionator l, which corresponds in boilingcharacteristics to the reflux condensate formed in this Zone, issupplied with the latter, as will be laterdescribed, to crackingtreatment in heating coil II, while any components thereof within therange of the overhead vaporous stream removed from fractionator 'I willbe commingled therewith and directed to further fractionatin treatment,as will be later described. .The oil supplied to heating coil I I istherein heated to thev desired cracking temperature at substantialsuperatmospheric pressure by means of .heat supplied from furnace I2within which the heating coil is disposed. The resulting heated productsare directed from coil I I through line I3 and valve I4 into the upperportion of reaction chamber I5 wherein the cracking reaction iscontinued.

Y Chamber I5 is also .preferably operated at a substantialsuperatmospheric pressure which may besubstantially the same or lowerthan that employed-at the outlet of coil II. Preferably, the reactionchamber is insulatedto conserve heat, although insulation is notindicated in the drawing.

. In the case here illustrated, both vaporous andliquid conversionproducts are withdrawn in commingled state from the lower portion ofchamber I5 and directed therefrom through line I6 and valve. II tovaporizing and separating cham-Y ber E8 which is operated atasubstantially reduced pressure relative to that employed in the reactionchamber. The liquid conversion products supplied to chamber I8 areappreciably further vaporized in this zone by virtue of the reducedpressure employed therein, leaving a nonvaporous residue in this zonewhich, depending upon the particular conditions of operation employed,may be either a liquid residue or substantially dry coke. When liquidresidue is produced in chamber I8 it may be directed from the lowerportion thereof through line I9 and valve to cooling and storage or tovany desired further treatment, not illustrated. When the process isoperated for the production of coke in chamber I8, a plurality of such.chambers are preferably employed, although only one is illustrated inthe drawing, so that they may be al,

Y previously described. Fractionator 'I is operated kto condensehigh-boiling components of the vaporouvsconversion products suppliedthereto and to separate therefrom as fractionated vapors, a lowerboiling stream comprising normally gaseous products, gasoline and alsoincluding, in this "particular instance, higher boiling fractions of thenature of light furnace oil. Redux condensate formed in fractionator 'Iis directed, together with corresponding fractions of any charging oilsupplied to this zone, from the lower portion of thel fractionatorthrough line 23 and valve 24 to pump 25 by means of which this materialis supplied, in the case here illustrated, through line I!) and valve 26to cracking treatment in coil VI I.

It is also entirely within the scope of the invention to supply onlycharging oil to heating coil II and to employ a separate heating coilfor selective cracking treatment of the reflux condensate formed infractionator 'I, although this modification is not illustrated in thedrawing. The system so far described, in conjunction with the drawing,is not considered novel per se and the advantages of the novel featuresprovided -by the invention are not dependent upon the specilc form ofcracking equipment employed therein nor its specific method ofoperation, except with respect to the aforementioned operation of thefractionating step. Many other modifications of the system so fardescribed may, therefore, be employed without departing from within thescope of the invention.

Fractionated vapors of the general character above mentioned aredirected from the upper portion of fractionator I through line 2l andsupplied, at least in part,'through valve 28 in this line to furtherfractionation in fractionator 29, a portion of the fractionated vaporousstream preferablybeing diverted from line 2l and subjected to furthertreatment, including partial condensation, Vas'will be subsequentlydescribed.

Simultaneous with Vtheoperation above described, another charging oil oflower boiling characteristics than that supplied to pump 3 and derivedfrom the same or separate source is separately subjected to crackingtreatment within the system. This secondary charging oil may be, forexample, straight-run or cracked gasoline, naphtha or the likecomprising gasoline fractions of inferior antiknock value which will bematerially improved by the type of cracking operation generally known asreforming. It -is supplied through line 3! and valve 3| to pump 32 andfed therefrom through line 33 and valve 34 to reforming in heating coil35. It is, vof course, within the scope of the invention to preheateither the relatively light or relatively heavy charging oil or both tobelow active cracking temperature by any well known means, notvillustrated, prior to their introduction into the cracking zone. v

-Heating coil 35 is disposed'in a furnace 36 byY means of which heat issupplied 'to the oil passing through the coil to heat it to the desiredrelatively high cracking temperature, preferably at a substantialsuperatmosphericrpressure. The resulting highly heated reformed productsare directed from. coil `.35 through line 3T and valve 38 and afterpreferably being cooled, as will be later described, .to atemperaturebelow that at which substantial further cracking thereof willoccur, they are directed through line 39 into fractionator 29, together-with Vfractionated vapors from fractionator 1.V Y j, Fractionator 29 isoperated to produce as a fractionated overhead vaporous stream from thiszone, the vapors having an end-boilingpoint corresponding to that of thedesired gasoline product of the process and to condense therein asreflui; condensate,.higher boiling 'components of the reformed productsfrom coil 35,'andY the fractionated vapors from fractionatorl Refluxcondensate thus vformed in fractionator 29 is withdrawn from( the lowerportion thereof through line 4I and is preferably directed in regulatedamounts through valve. 4.21m this line to pump 43V wherefrom. itisreturned to fractio-nator 29 via line. 94, coolorS, line 4B and line 39.The oil thus recycled commingles in line 39 with the hot reformedproductsY from coil 35 and serves as a means of reducing theirtemperature to the desired value. 'I'he function of cooler 45 is toreduce the temperature of the recycled reflux condensate in order tolimit thev quantity thereof which will be required to ac-A complish thedesired cooling. of the reformed products in line 39.

Fractionated vapors fof the desired end-boil;` ing point are directed`from the upper portion of fractionator` 29 through Valve 41, line 48and line 49 to condenser 59 wherein they are cooled suf-V iiciently toform a gas-containing distillate including substantially all of thegasoline fractions whereinl they are cooled sufficiently to form as theresultingdistillate, gasoline containing substantial quantities ofdissolved high-boiling gases. The Aresulting distillate is directed,together With the remaining uncondensed and undissolved gases throughline l and valve 52 to collection and separation in receiver 53.Distillate is Withdrawn from this zone through line 54 and valve 55 tostorage or to any desired further treatment, not illustrated, such as,for example, stabilization to reduce its vapor presl sure to the desiredvalue. Uncondensed and un'- dissolved gases-collected in receiver 53 aredi-f` rected therefrom through line 56 and valve 51 to storage or toabsorption treatment or elsewhere, as desired. When desired, regulatedquantities of the distillate collected in receiver 53 may b'ereturnedbymeans of line 58, valve 59, pump 6D, line El'and valve 62 tothe upper portion of fractionator 29 to servetherein as a cooling andrefluxingmedium.

Preferably, as previously mentioned, regulated quantities of theoverhead vaporous stream from` fractionator 1, instead of being suppliedto fractionator 29, are subjected to separate treatment for the purposeand in the manner which will now be described. These vapors are directedin the desired quantity from line 21 through line 63 and valve 84 tocooling and partial condensation in condenser 65- wherefrom theresulting distillate and uncondensed vapors and gases'are directedthrough line '66 and valve 61 to separa` tion in accumulator 68'. i

One of the purposes of subjecting regulated quantities cfr-'thefractionated vapors from fractionator I ltopartial condensation, asabove (1e-'- scribed, to form a distillate for' use as" cooling andrefluxing medium in fractionator 1 and, for this purpose, distillatecollectedv in accumu-` lator 68 is directed therefrom inregulated quamAtitles through line 69, valve 18, pump 1I,` line 12 and valve 13 to theupper portion of frac-:. tionator 1.

Anotherpurpose of the partial condensation treatment to whichfractionated vapors from fractionator 1 are subjected is to decrease theload which would otherwise be imposed upon the secondary fractionator 29if all of the fractionated vapors from primary fractionator 1 weresup'aV plied thereto. This is accomplished by socontrolling thetemperature and pressure conditions employed in partial condenser. andaccumu-A lator 68 that a substantial quantity of theA vae pors remainuncondensed in the accumulator and that the uncondensed 'materials willnot includeany appreciable quantity of fractions boiling above the rangeof the desired gasoline prod-z uct recovered in receiver 53. It will beunderstood that the features of the invention, last described, may beemployed to' advantage in many cracking systems wherein the vaporousconversion products are subjected to primary and secondary fractionationand that this aspect of the invention` is not limited to use in thecombination cracking an-d reformingsystem. That portion of the secondaryreflux condena sate formed in fractionator 29 which is not-recycled tothis zone, in the manner `previously described, after being used asacooling and reiluxingmedium `for the reformed products from coil 35 isdirected lfrom line 4| and through line 11 and may be directedtherefrom, all or in part, through line 18 and valve 19 tov cooling andstorage or to separate cracking treatment Within the same or a separatesystem or elsewhere, as desired. Preferably, however, this material isdirected, all or in part, from line 11 through line 88 and valve 8| intovaporizing chamber 82 which is preferably operated at a reduced`pressure relative to that employed in fractionator 29. Chamber 82 isoperated to effect sucient vaporization of the oil supplied thereto thatundesired light fractions, which would give it an especiallylow flashpoint for use as fur' nace oil, are liberated therefrom. In case thereduction in pressure employed in chamber 82 is not sufficient toaccomplish this, additional heat may be supplied to the unvaporized oilin chamber 82 in any suitable welll known manner and, in the particularcase here illustrated, a closed coil 83 `through which a suitableheating medium, `such as steam or hot oil derived from within orexternal to the system may be passed, is provided in the lower` portionof chamber` 82 to reboil the oilsupplied to this zone. remainingunvaporized in .chamber 82 isV directed through the lower portionthereof through line .84 and valve 85 and, in the specific opera-A tionunder consideration, this product is .cooled and recovered asspecification furnace oil. Light vapors and gases evolved in chamber 82from the oil supplied to this Zone are directed from the' upper portionthereof through line 86 and valve 8,1 to condenser 88 whereinsubstantially all of removed from the accumulator through line 9|- andvalve 92 and may be directed to storage `or The oir toabsorptionequipment, not illustrated, or elsewhere, as desired. Distillatecollected in accumulator 90 is `directed therefrom through line 93 andvalve 9# to pump- 95-wherefrom it isv fed through `line 96 and may bethence directed in regulated quantities through line 91 and valve 98into fractionator 29 wherein it comm-ingles with the vapors undergoingfractionation in this zone, serves as a cooling and refluxing mediumtherefor and is therein subjected to refractionation. When desired,ydistillate from accumulator 96 may also be employed in regulatedquantities as a cooling and refluxing medium in primary fractionator l.To accomplish this it is directed from line 96 through line 9,9 andvalve I to pump H and therefrom through line l2 and Valve 'I3 tofractionator 1.

As an example of one specific operation of the process provided by theinvention, as it may be conducted in an apparatus such as illustratedand above described, the charging oil amounts to 3160 barrels per streamday of which 2660 barrels is an Illinois reduced crude of approximately24" A. P. I. gravity, while the remaining 500' barrels is a straight-runnaphtha of approximately 51 A. P. I. gravity. f

The topped crude is supplied to fractionator 'I and passed therefromwith the reflux condensate formed in this Zone to heating coil l I thetotal feed supplied to this zone amounting to approximately 10,000barrels per day and being supplied thereto at a temperature ofapproximately 765 F'. Conversion products are discharged from coil Il ata temperature of approximately 935 F. and a superatmospheric pressure ofapproximately 2'75 pounds per square inch and are passed throughreaction chamber l5 which is operated at substantially the samepressure.

The total products from the reaction chamber are supplied to Vaporizingand separating chamber IB at a temperature of approximately 860 F. Thepressure employed in chamber I8 is approximately 270 pounds per squareinch, superatmospheric. The succeeding primary fractionator is operatedat substantially the same pressure and a reduced superatmosphericpressure of approximately 150 pounds per square inch is employed in thesecondary fractionator and the succeeding condensing and -collectingequipment.

In this particular operation the residual liquid removed from chamber I8is flash distilled at reduced pressure to produce specification fuel oilin flash distilling equipment of suitable well known form notillustrated in the drawing.

A top temperature of approximately 500 F. is maintained in the primaryfractionator and approximately 48 weight per cent of the overheadvaporous stream is supplied directly to the secondary fractionator. Theremaining portion of this stream is supplied to condenser 65 wherein itis cooled to a temperature of approximately 150 F., the resultingcondensed and uncondensed materials being collected and separated inaccumulator 68 which is operated at approximately the same pressure asthat employed in the primary fractionator and a temperature of about 150F. Distillate from accumulator 68 is returned in regulated quantities tothe upper portion of fractionator 1 to serve as a refluxing and coolingmedium and the uncondensed materials from accumulator B8 are commingledwith the stream of ,fractionated vapors being,

supplied from secondary fractionator 29 to condenser 50.

The naphtha charging stock is supplied to heating coil 35and thereinreformed, the outlet temperature from this coil being approximately.10.25 F. and the outlet pressure approximately 450 pounds per squareinch, superatmospheric. The reformed products are cooled to atemperature of approximately '700 F. and introduced into the secondaryfractionator which is operated at a superatmospheric pressure of about150 pounds per square inch.

' A top `temperature of about 400 F. is maintained in the vsecondaryfractionator and the fractionatedvapors from this zone, together withthe uncondensed materials from accumulator 69, are cooled in condenser59 to a temperature of approximately F., the resulting gas-containingdistillate and uncondensed and undissolved gases being supplied toreceiver 53 wherein they are separated. The distillate from this Zone issupplied to suitable stabiliz'mg equipment of well known form, notIillustrated, wherein its vapor pressure is reduced to approximately 10pounds Reidy by liberating therefrom regulated quantities of thedissolved gases. A regulated quantity of the distillate collected inreceiver 53 is returned to the upper portion of fractionator 29 to serveas cooling and reuxing medium in this zone.

Reflux condensate formed in the secondary fractionator is withdrawn fromthe lower portion of this zone at a temperature of approximately 550 F.and at the rate of approximately 530 barrels per day. Approximately 290barrels per day of this material is cooled in cooler 45 to a temperatureof approximately F. and then commingled in line 39 with the reformedproducts discharged from coil 45. The remainder is supplied withoutcooling to vaporizing chamber 82 which is operated at a superatmosphericpressure of approximately l0 pounds per square inch and wherein thesecondary reflux condensate is reboiled at a temperature of about 500 F.The remaining unvaporized material, amounting to approximately barrelsper day, is recovered as specification furnace oil and the evolvedvapors are subjected to condensation in condenser 88 at a temperature ofabout 95 F., the resulting distillate being returned from receiver 90 toa mid-.point in the secondary fractionator wherein it serves as acooling and refluxing medium.

The yields of the various products which may be expected from anoperation such as above described are approximately as follows: Thegasoline produced will amount to approximately 50.5 volume per cent ofthe total charging oil and constitutes a blend of reformed and crackedgasoline having an end-point of approximately 400 F., a Reid vaporpressure of approximately l0 pounds and an octane number ofapproximately 69 as determined by the motor method. The reformedgasoline in this blend may amount to approximately 85 volume per cent ofthe naphtha charging stock and the cracked gasoline may amount toapproximately 44 volume per cent of the topped crude. The fuel oilresidue produced may amount to approximately 41 volume per cent of thetopped crude of 33.4 volume per cent of the total charging stock and, inthis particular operation, has a viscosity of approximately 250 secondsSaybolt Furol at 122 F. The furnace oil recovered from chamber 82 has aflash point of approximately 150v F. and also meets marketspecifications for light furnace oil in other respects. It may amount toapproximately 5.4 volume per cent cf the total charging oil. Theremainder or approximately 10.7 volume per cent of the total chargingoil is accountable for as gas and loss.

It will, of course, be understood that operating conditions may bevaried considerably, depending upon the specific charging stockundergoing treatment and the desired characteristics of the products,Without departing from the scope of the invention and the foregoingexample should, therefore, not be construed as a limitation.

I claim as my invention:

1. The hydrocarbon oil conversion process which comprises cracking acharging oil of relatively high boiling characteristics to convert thesame into high yields of gasoline, separating resulting conversionproducts into vapors and nonvaporous residue, fractionating the vaporsin a primary fractionating zone to condense relatively high boilingcomponents thereof as primary reflux condensate, returning the latter tothe aforesaid cracking step, subjecting at least a portion of theresulting primary fractionated vapors including componentsl boilingabove the range of gasoline to cooling and condensation undertemperature and pressure conditions such that gases and light gasolinefractions remain uncondensed and to form a substantially gas-freedistillate, returning the latter to the primary fractionating step as acooling and refluxing medium, simultaneously subjecting a secondcharging oil of relatively loW boiling characteristics to conditions ofhigh cracking temperature at substantial superatmospheric pressure toproduce therefrom high yields of good antiknock gasoline, partiallycooling the resulting heated products to a temperature at whichsubstantial further cracking thereof is prevented and commingling thesame with the remaining portion of the fractionated vapors from theprimary fractionating step which include components boiling above therange of the desired gasoline product, subjecting the mixture tofractionation in a secondary fractionating step to condense therefrom assecondary reflux condensate components boiling above the range of thedesired gasoline product, cooling and commingling regulated quantitiesof said secondary reflux condensate with said highly heated products ofthe second mentioned cracking step to effect said partial cooling of thelatter, combining said uncondensed gases and light gasoline fractionswith the resulting fractionated vapors from the secondary fractionatingstep and subjecting the mixture to cooling and condensation, andrecovering the resulting distillate.

2. The hydrocarbon oil conversion process which comprises, cracking acharging oil of relatively high-boiling characteristics to convert thesame into high yields of gasoline, separating re-` sulting conversionproducts into vapors and nonvaporous residue, fractionating the vaporsin a primary fractionating step to condense relatively high-boilingcomponents thereof as primary reflux condensate, returning the latter tothe aforesaid cracking step, simultaneously subjecting a second chargingoil of relatively low-boiling characteristics to conditions of highcracking temperature at substantial superatmospheric pressure to producetherefrom high yields of good antiknock gasoline, partially cooling theresulting heated products to a temperature at which substantial furthercracking thereof is prevented and commingling the same with fractionatedvapors from said primary fractionating step which include componentsboiling above the range of the desired gasoline product, subjecting themixture to fractionation in a secondary fractionating step to condensetherefrom as secondary reflux condensate components boiling above therange of the desired gasoline product, cooling and commingling regulatedquantities of said secondary reflux condensate with said highly heatedproducts of the second mentioned cracking step to effect said partialcooling of the latter, subjecting another portion of said secondaryreflux condensate to further vaporization to substantially free the sameof undesired light ends and leave an unvaporized portion meeting marketspecifications for furnace oil, recovering the latter, cooling andcondensingsaid vaporzed portion and supplying resulting distillate tothe secondary fractionating step as a cooling and refluxing medium, andsubjecting fractionated vapors of the desired end-boiling point fromsaid secondary fractionating step to condensation and recovering theresulting distillate.

3. The hydrocarbon oil conversion process which comprises, cracking acharging oil of relatively high-boiling characteristics to convert thesame into high yields of gasoline, separating resulting conversionproducts into vapors and nonvaporous residue, fractionating the vaporsin a primary fractionating step to condense relatively high-boilingcomponents thereof as primary reflux condensate, returning the latter tothe aforesaid cracking step, simultaneously subjecting a second chargingcil of relatively low-boiling characteristics to conditions of highcracking temperature at substantial superatmospheric pressure to producetherefrom high yields of good antiknock gasoline, partially cooling theresulting heated products to a temperature at which substantial furthercracking thereof is prevented and commingling the same with fractionatedvapors from said primary fractionating step which include componentsboiling above the range of the desired gasoline product, subjecting themixture to fractionation in a secondary fractionating step to condensetherefrom as secondary reflux condensate components boiling above therange of the desired gasoline product, cooling and commingling regulatedquantities of said secondary reflux condensate with said highly heatedproducts of the second mentioned cracking step to effect said partialcooling of the latter, subjecting another portion of said secondaryreflux condensate to further vaporization to substantially free the sameof undesired light ends and leave an unvaporized portion meeting marketspecifications for furnace oil, recovering the latter, cooling andcondensing said vaporized portion and supplying resulting distillate, inpart, to the primary fractionating and, in part, to the secondaryfractionating step, as a cooling and reluxing medium, and subjectingfractionated vapors of the desired end-boiling point from the secondaryfractionating step to cooling and condensation and recovering theresulting distillate.

JOI-DIW. WARD.

